This invention relates generally to medical imaging, and more particularly, to methods and apparatus for rapidly extracting relevant image data from a three-dimensional volumetric data set.
A challenging problem in the area of volume visualization is the ability to extract relevant information contained within a volume of image data, for example, medical image data, in a timely fashion using a method that is simple and intuitive to an end-user.
Volume rendering (VR) is a preferred choice for visualizing a volume of medical image data. The VR process is governed by a set of curves, namely opacity and color/intensity curves. These curves determine what contribution and color intensity a given voxel (a data point within the volume) will have in the resultant 3D projection or rendering. The challenge is to determine an appropriate curve to accentuate important information (such as by providing contrast enhanced vessels, for example) for study while suppressing irrelevant information to the study (for example, scanner table and bone structures in a study of vessels). Volume clipping or cut planes also can be used to remove portions of a volume that are not of interest and that would otherwise obscure or occlude relevant tissue or anatomy. For example, volume clipping can be used to cut away an image of a rib to get an unobscured sagital view of an aorta.
A problem with known systems for rendering volumes of image data is that they are either too slow to provide immediate feedback in medical or surgical environments, or they require powerful and expensive image processing hardware. Moreover, some known software-based volume renderers attempt to achieve faster interactive rendering by skipping large portions of an image volume. In a sense, the rendering process is tuned to particular voxel values given a volume rendering opacity curve. Portions of a volume that would be transparent (i.e., those range voxels values that have been assigned an opacity of zero) are not sampled. This scheme does not allow a user to adjust an opacity curve while the user is interactively being shown results of the adjustment.
It would thus be desirable to provide an interactive volume rendering capable of operating on relatively inexpensive hardware. For at least some medical or surgical uses, it would also be desirable to provide interactive controls that have a rapid response to reduce the time required for analysis of images. It would additionally be desirable that the response be so rapid that an operator of imaging equipment could interactively emphasize important information within the volume while maintaining essentially instantaneous visual feedback to guide his or her selection. Preferably, such interactive xe2x80x9ctweakingxe2x80x9d or adjustment to initial, protocolized settings to extract relevant data should require no more than about one minute per examination. It would be desirable to spend much less time on 3-dimensional parameter adjustments and xe2x80x9ctweaksxe2x80x9d so that final, full-fidelity renderings can be started much sooner than is done using current systems. To further increase clinical productivity, it would also be desirable to eliminate significant complexity in user interfaces, and provide an intuitive approach for systems to quickly extract relevant data from a volume.
One embodiment of the present invention is therefore a method for rapid extraction and visualization of relevant data from a volume of image data, the method including steps of rapidly producing reduced-fidelity images derived from an image volume, the reduced fidelity images having an adjustable visual parameter; adjusting the visual parameter of the reduced-fidelity images during the rapid production to select a desired adjustment; producing a full-fidelity image derived from the image volume; and applying the selected adjustment to the full-fidelity image.
This embodiment provides interactive volume rendering capability with relatively inexpensive hardware, with rapid response to reduce the time required for analysis of images.